Genetic factors are important in the development of glioma. Interleukin-12 (IL-12) is a multifunctional cytokine that induces Interferon (IFN)-gamma secretion and plays an important role in antitumor immunity. Interleukin-27 (IL-27) is a novel IL-12 family member, and the present studies demonstrate that IL-27 mediates a potent antitumor activity. The aim of this study was to investigate whether IL-12 and IL-27 gene polymorphisms and their serum levels are associated with glioma. We analyzed IL-12 gene 16974 A/C and IL-27 gene -964 A/G, 2905 T/G, and 4730 T/C polymorphisms in 210 patients with glioma and 220 matched controls, using polymerase chain reaction-restriction fragment length polymorphism method and DNA sequencing methods, while serum IL-12p40 and IL-27p28 levels were measured by enzyme-linked immunosorbent assay. Serum IL-12p40 and IL-27p28 levels were decreased in patients with glioma compared with controls (p < 0.01). There were significant differences in the genotype and allele frequencies of the IL-12 gene 16974 A/C polymorphism between the group of patients with glioma and the control group (p < 0.05). Moreover, genotypes carrying the IL-12 16974 C variant allele were associated with decreased serum IL-12p40 and IL-27p28 levels compared to the homozygous wild-type genotype in patients with glioma. The IL-12 gene 16974 A/C polymorphism may regulate expression of the serum IL-12p40 and IL-27p28, and associate with increased risk of glioma. Thus, genotypes carrying the IL-12 16974 C variant allele had a decreased ability to produce IL-12 and IL-27, which may contribute to glioma susceptibility.